What is the problem of desertification?

There are many lists of the problems with desertification. If you want more you can find it in the Internet or Google.

• One quarter of the earth's surface is threatened by desertification -- an area of over
3.6 billion hectares.
• Since 1990, 6 million hectares of productive land are lost every year due to land
degradation.
• The world's drinking water supplies have fallen by almost two thirds since 1950.
• Every year, 12 million people die as a result of water shortages or contaminated
drinking water.
• Desertification threatens the livelihoods of one billion people and has already
made 135 million people homeless.
• Every year, desertification generates income losses totalling USD 42 billion.
• One of the basic premises of the UNCCD is that land degradation is both a cause
and a consequence of rural poverty. Therefore, desertification makes for poverty,
and poverty makes for further desertification